freeze on startup

[hillsoftn]

Thanks in advance for your help

I was looking to add more ram or faster processor to son's computer.  Opened it up to see what kind he had.  Did not have any faster processor or compatible ram so nothing was added.  When he put it back together and booted, error message said Technical problem, must shut down system to prevent any damage to your computer.  When he shut it down and restarted, it now stops at the Dell screen.  The keyboard works only momentarily then stops.  Opened it up and recheck and reseated ram and processor.  Still stuck on Dell screen.  Can get into CMOS but then keyboard freezes and will not continue.  What have I done :-?

[Dilbert]

This sounds like the CPU is overheating. Dells are horrible in this way: The heatsink tends to draw in a lot of dust. Opening the case and fiddling around could have knocked some dust in the air, only to be sucked in by the fan. Try this: Open the case back up. Compressed air is recommended, otherwise you'll need to use your own lungs for this. Blow/blast as much dust from all the fans inside as possible, especially the one above the processor, and reboot.

[hillsoftn]

   Thank You, Thank You, I love any easy fix.  

[Dilbert]

You're welcome.